Electrical switch



Aug. 28', 1951 f J. s. LINN ELECTRICAL SWITCH Filed Jan. 3l, 1949 2 Sheets-Sheet l 1N VEN TOR. QOME S. L/N/v,

zum 1 TTOQNEY,

Aug, 2s, 1951 J. s. LWN 2,565,863

ELECTRICAL SWITCH Filed' Jan. 3l, 1949 2 Sheets-Sheet 2 24o/n1. ANGLE -9- :j-ROME A5. 1N/v,

IN VEN TOR.

Patented Aug. 28, 1951 ELECTRICAL SWITCH Jerome S. Linn, Los Angeles, Calif., assigner to Elcon Mfg. Co., Los Angeles, Calif., a corporation of California Application January 31, 1949,'Serial No. 73,727

3 Claims.

'This invention relates generally to improved electric switches having novel structural characteristics rendering them especially desirable for use in aircraft and under other similarly exacting conditions.

A major object of the invention is to provide a switch relatively smaller and more compact than other switches of corresponding capacity and effectiveness. For this reason, I employ a novel spring arrangement especially designed to act both as a contact shifting member and as a means for urging the contacts into tight engagement in circuit closing position. Preferably, the spring takes a double bowed form, a movable contact being carried by the spring intermediate its two bowed ends.

It is a further object of the invention to provide an extremely simple switch having a movable contact adapted to snap suddenly from one position to another irrespective of the rate at which the control element or handle is actuated.

To eifect this purpose, I employ stationary and movable contacts having inter-engaging irregularities acting to releasably retain the movable contact against displacement during the first part of a shifting movement and until enough energy has been stored in a shifting spring to result in the defined snap action. The movable contact may be cylindrical in form and receivable within a partial cylindrical recess in one or more stationary contacts.

I also provide a novel member adapted to assure shifting of the movable contact upon movement of the control element if the spring fails to cause such displacement. This member may be U-shaped to straddle a central hub of the movable contact and displace that hub by movement in either direction.

The invention affords a unique type of contact movement resulting in effective wiping of the contact surfaces during the rst period of handle movement in any direction and before the movable contact commences its travel away from the stationary contact. This novel wiping action results from slight rotation of a cylindrical contact within an engaging cylindrical recess in another contact, and is caused by the novel spring drive. To maximize the wiping rotation, I preferably employ an additional spring or strap loosely carried by a main double bowed spring and movable relative to that bowed spring during the rst stages of shifting motion.

The present invention may be embodied in a sustained contact switch or in a momentary contact switch, that is, one in which the movable 2 parts return to a normal position as soon as the control element or handle is released. Novel yielding meansv are used if such momentary contact is desired, these means preferably comprising an H-shaped overriding spring bearing against the switch body to urge the movable contact to normal position.

It is often desirable, where widely varied environmental conditions are to be encountered, to hermetically seal the outer case of a switch in order to protect its mechanism against injury from the environment. In the present invention, I employ means for effecting such sealing while permitting complete freedom of motion of the operating handle or lever and the other moving parts. For this purpose, I disclose a flexible sealing element to be secured about a control element and to the switch housing about the periphery of an opening through which the control element passes. In accordance with the invention, the sealing element may take the form of a flexible annular diaphragm which is desirably retained at its inner edge between a pair of hemispherical sections serving together as a toggle ball. It is contemplated that the diaphragm/will take an optimum form having such shape and material distribution as to minimize stress in all positions of the handle or control element.

The above and further features and objects of the present invention will be better understood from the following detailed description of the typical embodiment illustrated in the accompanying drawings, in which:

Fig. 1 is a side View of the switch with its side wall broken away and with a portion of the base broken away to disclose three of the stationary contacts;

Fig. 2 is a transverse section taken on line 2--2 of Fig. 1 and showing one portion of the movable contact in section and the other portion in elevation;

Fig. 3 is a section taken on line 3-3 of Fig. 2;

Fig. 4 is a section taken on line 4-4 of Fig. 3;

Fig. 5 is an enlarged fragmentary section taken on line 5-5 of Fig. 2;

Fig. 6 is an enlarged fragmentary section showing the sealing diaphragm and its means of attachment to the switch case and operating mechanism;

Fig. 7 is a schematic representation of the movable contact and a stationary contact showing, in exaggerated form, their different radii of curvature;

Fig. 8 is an enlarged elevation diaphragm;

of the .contacts .23, .29,

Fig. 9 is a graphical representation of the optimum circumferential contour of the diaphragm; and

Fig. 10 is a perspective View of one corner of the switch base.

The single pole 3-position switch represented in the drawings comprises essentially a substantially rectangular case I9, 'a contact vand terminal carrying base II, and movable control mechanism, generally indicated at I2. The case is open at its lower side as seen in Figs. l through 3, to provide an opening for reception of therbase. Upper wall i3 of the case carries face plate I3 suitably secured to the case as by spot welding at I4 and I5. end plate I 3 have corresponding elongated openings or slots I3 and I1 extending longitudinally of the switch, and are deformed in opposite directions about those openings to form angularly disposed annular portions I9 and 20 which provide space for 4the reception of diaphragm I8 and serve as retaining means for the movable mechanism later to `be described. The upper vsurface of the case is downwardly offset from the plate outwardly of portion .I9 and 2G to.

form a narrow annular space 2| between the plate and case and within which the periphery of the diaphragm is clamped. The opposed'surfaces Yof plate I3 and the upper wall of the case vare notched at 22 within space 2! 'to assure a positive seal and prevent displacement of the diaphragm. The diaphragm is annular in configuration, as seen in Fig. 8, and is retained inwardly by the movable mechanism in a manner -later to be described. Openings 23 and 24 in the face plate permit mounting of the switch on a control panel or other support.

Base I is molded of Vsuitable insulating material, preferably high strength asbestos filled plastic. The base `presents an angularly -disposed outwardly facing wedge surface 24 of essentially rectangular horizontal section and adapted to be forced into the open lower end of case I@ Yagainst the inner surface of its side walls 21 to maintain the case and base in assembled relation and to provide a fluid tight seal between them. This seal may be augmented by the application of a bonding cement before forcing the two parts together. Peripheral ange 25 on the base engages the lower surface 29 of the case side walls 21-with the base in assembled position. As seen in Fig. l0, each of the four corners of the base has a recess 95 at its point of engagement lwith the `case into which the adjacent portion of the case is peened to -further assure retention of the two parts in correct assembled relation.

The various stationary contacts and Aterminals .are Amolded into the base during its formation.

.At one-side-of the longitudinal center linedesignated by section line 3 3 in Fig 2, threesta- .tionary contacts .23, 29 Vand 39 are accurately `disposed in upwardly .facing positions (see Fig. l). `Each of thesecontacts presents a vpartial cylindrical upper contact surface SIlengageable by a cylindrical .movable -contact later to be described. The base itself presents non-.conduct- .ing surfaces SI between the adjacent contacts of the above three and beyond the Aend ones to form, with the contacts, a more or less con- '1 tlnuous accurate surface having va slight recess at each contact. Terminals 32, 33 Vand 34 extend upwardly through the base to electrically engage and .30, respectively. At their lower The upper wall'of :the case and exposed ends, these terminals present 'i` .tacts 28, 29 and 39 (sce Figs. 3

.to-bridge them. On its lower surface, terminal 42 .presents opening 43, within which screw 41, carrying washer 48, is threadedly received.

Thin insulating spacer 49 is molded into the base during its formation in depending relation vztosthe base, and extends longitudinally along its center line between the lower portions of ter- .mnals 32, 33 and 34 on one side, and terminal 42- on thefother side .to prevent any direct electri- .cal'connection betweentheseterminals. At the top of the base, insulating guide 50 having a bottom 92 and a pair of U-shaped side walls 93, is retained in upstanding position between .contacts 23, 29 and .30.and the upper ends of their associated terminals at oneside, andcontacts 43, 44 -and 45 and terminal 42. The plastic base is recessed at 5I forthe reception ofguide 50. vAt each end beyond,the-stationarycontacta .the base presents a pair of substantially horizontal upwardly facing shoulders 52,.one to either side of guide 5I).

As shown in exaggerated form .in Fig. 7, the common radius of curvature ofthe partial cylindrical surfaces '9u on the faces of the outer surfaces of the stationary contacts is somewhat larger than that of theouter surfaces Vof .the movi able contact, in order to assure satisfactory elecvjacent .its upper surface 58.

trical engagement. The dashed lineof Fig. 7 represents the curvature of the surfaces on the stationary contacts.

Movable mechanism I2 isbuilt up around npin 5.3, which .extends upwardly through openings I6 and vI1 in the case and face plate. The lower end of this pin isknurled at 54 and molded within 'opening'55in U-fshapedV positive action tyoke 56,

l BI have upper enlarged circular portions 62 and 53, respectively, with openings of size and shape corresponding to the sectional configuration of surface 51 and are receivable about that surface. Washer 64 has a similar opening and is received about surface 51 above the springs. As will be understood, engagement of the non-cylindrical portions 59 of surface 51 with the openings of springsf and '6I and washer 64 serves to'key the springs in the illustrated positions relative to'yoke 55.

insulating washeris received about Vpin '53 above yoke56 to engage its upper surface 58 and washer 64. Such engagement of washer 64 serves to rigidly retain the two springs against displacement from'the yoke.. Toggle ball sections '66 and 61, have openings 9E and 91 of internal diameters corresponding to the external diameter of the pin, are lreceived vabout vthe pin above washer .35. Handle 68 is lthreadedontovthe upper end'of the pin'at S9 :tolurgefall Aof thepartsrcarried by the pin downwardly against yoke 55 and thus form a single movableunit including the handle, pin, ball sections, washer, yoke, and springs Bil and 6|. Upper ball section 61 has a slightly enlarged internal diameter at 1I extending upwardly from its bottom to form an annular recess within which the inner portion of the diaphragm is clamped to form a first fluid tight seal. The next adjacent outer portion of the seal is clamped between the opposed horizontal surfaces of the two ball sections to afford a second uid seal. The ball sections present complementary outer partial spherical surfaces 94 engageable with the inner partial spherical surfaces 12 of plate I3 and upper wall 13 of the case. Such mounting of the movable mechanism, that is by engagement of the ball sections with surfaces 12, permits pivotal movement of handle 68 between the central full line position of Fig. 1 and the two positions illustrated in dot-dash lines.

Spring 60 presents a bowed portion 13 at either end, and is preloaded in the position of Fig, 3 to urge the free hooked ends 14 downwardly. U- shaped strap or spring 15 has similarly hooked ends 16 loosely engaging ends 14 of spring 6D, and is thus urged downwardly also. Both spring 6i) and strap 15 are of such width as to permit the reception of their lower portions between walls [43 of guide 59, which thus serve to insulate the springs from the stationary contacts and terminals (see Figs. 2 and 4).

Movable contact 11 is carried, at its central hub portion 18, by strap 15. At each side of this hub portion, contact 11 has an enlarged diameter portion 19, carrying a cylindrical contacting portion M. As will be understood, the movable contact is displaceable between three positions of bridging engagement with the various stationary contacts. For instance, in the central position shown in the drawings, the two cylindrical portions 83 of the movable contact engage the central stationary contacts 29 and 44 to close a circuit between these two contacts through hub portion 18. Similarly, the movable contact may be displaced to a position of bridging engagement with contacts 2B and 43 or contacts 39 and 45. Pivotal movement of handle B8 serves to effect such displacement through double spring El?.

If it is desired that the switch be of the sustained contact type, overriding spring El need not be employed. That spring is to be used only in case the switch is intended to be of the momentary action type, in which the central position is the normal one, and the switch automatically returns to that position after release of the handle. Spring 6| is substantially H-shaped (see Fig. 4) with the previously referred to portion 63 forming its cross piece, and presents downwardly curved outer extremities or legs 3l straddling spring 6U and insulating guide 50 and engageable with the four upper surfaces 52 of the base. Any movement of handle 68 resiliently deforms the two legs of spring 6| at one end of the switch and moves the legs at the other` end upwardly against the top wall of the case in a manner such that all four of the legs act together to urge the switch toward its normal central position.

From the foregoing description, it will be evident that spring 60 carries out the dual functions of urging the movable contact into tight engagement with the stationary contacts in any of the three positions of the switch, and serving as a contact displacing or drive member. During the initial stages of handle movement between any two of the three positions shown in Fig. 1, engagement of the cylindrical movable contact with two corresponding stationary contactsrprevents immediate displacement of the movable contact and stores energy within spring as a result of its deformation by the handle. At a predetermined stage in the handle movement, the energy stored within the spring is suiicient to overcome the detent action of the contacts and effect a sudden snap movement of the movable contact between positions. Such snap action minimizes sparking and resultant contact deterioration. If, for any cause, the movable contact is not displaced by spring 6U, one of the inner surfaces 82 of element 56 engages strap 15 to positively displace the movable contact in the desired direction. Spring 6| urges the handle and associated movable parts toward the centered position at all times, and returns the switch to this normal condition when the handle is released.

Because of the novel construction of spring 60 and its loose connection with strap 15 through hooked ends 14 and 16, movement of the handle causes rotation of the movable contact before it is laterally displaced. This rotation results in an effective contact wiping action which cleas the surfaces of the contacts in response to each switch operation. Specifically, movement of the handle tends to lower one side of spring 6B and thus pivot strap 15 about the axis of the movable contact, and in turn to rotate that contact, An additional wiping action results from the lateral displacement of the movable contact oi of the stationary contact during its snap movement between positions.

Leads from the circuits to be controlled are secured to terminals 32, 33, 34 and 42 by the terminal screws. The switch normally closes the circuit between terminals 33 and 42 but breaks that circuit and temporarily closes another between terminals 32 and 42 or 34 and 42 when the handle is actuated to one of the dot-dash positions. Though I have described the invention as embodied in a three on position single pole switch, its novel aspects may obviously be incorporated in switches with other contact arrangements.

Since diaphragm I8 must be deformed upon each movement of the switch, I form that diaphragm with such predetermined material distribution and shape characteristics as to minimize the stress to which it will be subjected and consequently lengthen its active life. It is intended that, for any switch embodying the invention, the optimum size and shape will be calculated in accordance with known mathematical methods which need not be discussed in detail here. I have calculated the most desirable arrangement for a circular diaphragm of Athe type shown in the drawings with a handle throw (angle a of Fig. 1) of 25 degrees, and will briefly note the results.

The material distribution in the diaphragm must be such as to induce minimum stresses and good stress distribution with the handle in the center or either of the thrown positions. The shape and material distribution for optimum stress conditions with the handle centered differs from the shape and material distribution for optimum stress conditions with the switch thrown. The difference in these ideal material distributions is a function of the ratio of the inside clamping diameter B (see Fig. 8) to the outside clamping diameter C. As the inside diamvbe straight lines.

'eter becomes small and the ratio approaches zero, the material distribution difference approaches zero.

The optimum material distribution canvbe described by reference lto two contours, a radial contour and a circumferential contour. The

radial contour is. mostappropriately taken along the line of action of handle 98, that is, along line '83 of Fig. 8, and is represented in enlarged section by Fig. 6. The circumferential contour is best taken at approximately the middle of the unclamped diaphragm area, i. e., along line B4 of Fig. 8.

The optimum radial -contour along the line of action with the switch in one of the thrown positions, that is with the handle in a dot-dash position of Fig. 1 or Fig. 6, takes the form of a lsine function slightly greater than 270 degrees :inlength and is represented by curve 85 of Fig. 6. The ideal shape in the centered position would, of course, be a iiat disc, in which case the radial and circumferential contours would both The ideal unclamped length of material along the line of :action to prevent excessive stress in any of the three positions is intermediate the amount Arequired to permit the assumption of a 270'degree sineshape :in thrown position and that required to 'forma fiat disc in centered position. The -most .desirable value is .approximately the rmean of these two, and takes vthefullline form of Figf incenter position and thedot-dash shape in thrown position.

The ideal circumferential contour in thrown position takes the approximate form of a cosine curve with reverse curvature, starting from the line of action, and is represented-byourve- 86 in thefgraph of Fig. 9, being the-radial angletaken from the line of action l83 in Fig. 8. The optifmum circumferential contour for a diaphragm vin centered position, assuming the-use of .-a shape other than a -at disc and 'assuming that the diaphragm will extend in substantially a straight line from sideto side, that is alonglinef-S'I of Fig.

.2. .-'A :switch .comp-rising .a :movable operating element, =a spring vhaving a pair of oppositely bowed portions carried by said element for movement thereby, said portions terminating outwardlyfinxoppositely,disposed free ends, a substantially .U-.shaped -fyoke carriedby and between said free -ends'of the spring, a stationary contact and a movable contactcarried by said yoke and urged 'by .the-*tension of said bowed spring portions into engagement 4with said stationary contact in one fposition of the switch, one of said contacts having recess within which the other contact is partially receivable in said position of the switch 'to releasablyretain said/movable Contact against relative lateral displacement, whereby movement 'of said Loperating element tending to laterally displace said movable contact eifects initial dis- "tortion of said Ybowed portions of the spring 8, is a 90` degree-cosine function, represented by element, a spring having a ,pair .of oppositely -.bowed portions carried by said-element for moveiment thereby, vsaid portions vterminating 'out- -wardly in oppositely'disposed free ends, a member loosely'carried by and between said free ends of the spring, a stationary contact vand a Vmovable contact carried by said member and urged 4by the tension of said bowed spring portions into engagement with said stationary contact in one positionof the switch,- one of said contacts having a recess within which .the other `,contact is partially receivable in saidposition of the switch utoreleasably retain said movable contactagainst relative lateral displacement, whereby movement of said operatingelernent tending to -laterally displace said movable contact-effects initial Vdistortion of said bowed portions of the spring .followed by sudden movement of said movable contact vfrom engagement with said .stationary contact.

followed `.by sudden movement of said movable contact from engagement .with said stationary contact.

3. A switch comprising a movable operating element, a spring having a pair of oppositely vbowed portions carried by said elementfor movement thereby, said portions terminating outwardly in oppositely disposed free ends, a substantially U-shaped yoke carried by and between said free'ends of the spring, a stationary Contact, and

va movable contact carried by said yoke and urged by the tension of said bowed spring portions into engagement with said stationary contact in one position of the switch, one of said contacts having arecess within which the other contact is partially receivable in said .position of the switch to releasably retain said movable contact against relative lateral displacement, whereby movement of said operating element tending to laterally displace said movable contact effects initial distortion of said bowed portions of the spring followed by sudden movement of said movable contact from engagement with said stationary contact, said free ends ofthe spring and said U- shaped-yoke being connected by loosely interengagedandxrelatively'movable'hooked portions.

JEROME S. LINN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number l Name Date 561,581 Guett June 9, 1896 1,146,326 Gordon July 13, 1915 .1,666,925 BenjaminA et al. Apr. 24, `1928 1,814,777 Wurdack, Jr. July 14, 1931 1,892,537 .Prager Dec. 27, 1932 2,015,399 Grothe Sept. 24, 1935 2,247,195 Frank et al June 24, 1941 2,334,901 YBullerjahn Nov. 23, 1943 2,440,943 Gonsett etal May 4, 1948 2,448,841 Taylor Sept. 7, 1948 2,469,336 Kohl May 3, 1949 v2,476,784 Wahlstrom July 19, 1949 FOREIGN PATENTS Number Country Date 764,857 France May 29, 41934 

